1. Field of the Invention
This invention relates generally to the amplification of stringed instruments and, more specifically, to an Exchangeable Stacked Pickup Assembly and Installation for Stringed Instruments.
2. Description of Related Art
Electromagnetic field-type pickups have been available for stringed instruments for a number of years. In the case of guitars, virtually every contemporary musical group uses one or more guitars equipped with an electromagnetic pickup. In fact, many musicians own more than one model or type of "electric guitar" in order to obtain different sounds for different musical pieces. Alternatively, the musician may have guitars of the same model, but with different electromagnetic pickups in each. It is this necessity for different guitars to obtain different sounds that is the focus of the present invention.
FIG. 1 depicts a conventional electric guitar 10. While available in a wide variety of configurations, the typical electric guitar 10 design includes a plurality of typically metallic strings 12 running from the head 14 to the bridge assembly 16. The strings 12 are located cooperatively with one or more pickups 18, such that the pickups 18 will detect vibrations in the strings 12 and convert these vibrations into an electrical current for external amplification and other adjustments.
FIGS. 2A-2D depict common designs for pickups 18. FIG. 2A depicts a conventional single coil pickup 20. Located within the pickup 20 is a single electromagnetic coil 22 and a plurality of pole pieces 28, creating a magnetic field therein. FIG. 2B shows a conventional dual coil pickup 24, having a pair of coils 22. As shown in FIG. 1, the pickups 20 and 24 can be oriented in various positions in relation to the strings (see FIG. 1). FIG. 2C shows a single coil pickup 20, similar to the pickup of FIG. 2A, but with a single bar magnet 23 in place of the plurality of pole pieces 28. FIG. 2D shows a double coil 29, in which there is a single coil winding 32, separated by insulating pieces 26, and in which there may be two different types of magnets 23.
Now turning to FIG. 3, we might better appreciate a common prior coil 22. As can be seen, this coil 22 comprises a pair of insulating plates 26 through which a plurality of pole pieces 28 pass. In this design, the pole pieces 28 are magnetized such that either end has opposite polarity. The polarity arrangement will create a magnetic field between the ends of the pole pieces 28, depicted by the field lines 30. It should be appreciated that the strings 12 pass through the magnetic field lines 30 as they pass over the coil 22. Not all pole pieces 28 have the same magnetic qualities; different magnetic characteristics and/or materials will result in different fields 30 (or field strengths) for each particular string 12 and pole piece 28 combination. The coil 22 also has coil windings 32, which are, essentially, formed from a thin, continuous wire wrapped around the pole pieces 28. The coil windings 32 pass through magnetic fields 30 of all of the pole pieces 28, and could be made from a variety of metallic materials, depending upon the desired sound.
In operation, therefore, vibrations of each metallic string 12 will create fluctuations in the magnetic field 30 of the associated pole piece 28. Fluctuations in magnetic field lines 30 are well known to create electromotive forces resulting in electrical current in any electrical wires located in and perpendicular to the field lines 30. As a result, the vibrations created when a musician strums the strings 12 will cause fluctuations in the magnetic fields 30 associated with that string 12, and a current or voltage will be created in the coil windings 32 that is then used by amplifiers and other devices to produce external sound through speakers.
FIG. 4 gives further detail regarding the prior art. FIG. 4 is a cutaway side view of the coil 22 of FIG. 3 as it might be installed within an electric guitar. As can be seen, the pole pieces (see FIG. 3) typically comprise a pole core 34 sheathed in a pole insulator 36, both of them passing through the two insulating plates 26. It should be appreciated that the pole insulator 36 and insulating plates 26 may be combined into a single frame for the coil windings 32 (known as a "bobbin"). The coil 22 is either surface mounted on the face of the guitar 38, or it may be located in a recess 40 formed within the face 38, depending upon the particular guitar design. The coil 22 is installed such that the pole distance 42 is adequate for the strings 12 to vibrate freely, while also providing optimum sound output; this distance 42 is determined by the guitar design, and may be adjusted to some extent by the musician.
It can be easily understood that different numbers of coil windings 32 (and therefore wire lengths) that are on the coil 22 will result in a different characteristic sound for that particular coil 22. It should be appreciated that the pole distance 42 is insufficient to permit the coil 22 to be removed without first removing the strings 12. This can be a very time-consuming process, which is why musicians maintain more than one guitar. The design depicted in FIGS. 3-4 are exemplary only; a wide variety of other designs are known, including designs that combine insulating pole pieces 28 and magnets located elsewhere in the coil 22. What all have in common, however, is that the amplification of the sound is created by currents or voltages created in the coil windings 32, and that to change the guitar's sound characteristics, one must change either the magnetic qualities of the pickup or the number of windings in the coil 22, or both.
What is needed, therefore, is a pickup system for stringed musical instruments that permits the user to change magnet characteristics and/or the number of coil windings without necessitating string removal and subsequent guitar re-tuning.
Lace, U.S. Pat. No. 5,221,805 sought to solve this problem. The Lace device is, essentially, a secondary magnet that is added on to the top of an existing pickup. Lace states that the "add-on device . . . modifies the operating characteristics . . . of the output signal of an electromagnetic pickup" by changing the apparent characteristics of the pickup's magnetic field. The problem with the Lace device is that it is limited in its range. While changing the characteristics of the magnetic fields should result in some change in the output signal, it will not permit the large changes available by changing the number of coil windings, the coil wire diameter, or the coil wire material. If a musician could change either the magnetic field or the coil characteristics (i.e. number of windings, wire diameter or material), or both, without needing to re-string the musical instrument, that musician would truly be able to obtain virtually any desired sound out of a single musical instrument.